A steering system is required to control the direction of travel of a vehicle. Typical mechanical steering systems include a mechanical linkage or a mechanical connection between a steering input device and a steering output device. The steering input device (e.g., a hand wheel and steering column) is connected to the steering output device (e.g., steerable road wheels) via an articulated mechanical linkage. Thus, movement of the hand wheel causes a corresponding movement of the steerable road wheels to control the vehicle's direction of travel.
These mechanical steering systems are being replaced and/or supplemented by electrically driven steering systems, commonly referred to as “steer-by-wire” systems. Steer-by-wire systems typically comprise a steering input device, a plurality of sensors, an electronic control unit, an actuator, and a steering output device. The position of the steering input device is detected by one of the sensors. The sensor converts the position into an electrical signal and provides the signal to the electronic control unit. Based upon the electrical signal, the electronic control unit operates the actuator to change the position of the steering output device. The actuator is, for example, an electric motor or hydraulic actuator. Thus, the electronic control unit controls the actuator to adjust the position of the steering output device based upon the position of the steering input device.
The migration to steer-by-wire systems has made new steering input devices possible. The migration to steer-by-wire systems has also made new safety devices possible, as well as allowing the implementation of current safety devices to be revisited.
Accordingly, there is a continuing need in steer-by-wire systems for improvements in the steering input devices and the available safety devices.